Avies JS31 at Kardla on Oct 28th 2013, rejected takeoff after runway excursion

Last Update: June 11, 2015 / 15:31:12 GMT/Zulu time

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Incident Facts

Date of incident
Oct 28, 2013

Classification
Incident

Cause
Rejected takeoff

Airline
Avies

Flight number
U3-2082

Departure
Kardla, Estonia

Destination
Tallinn, Estonia

Aircraft Registration
SE-FVP

Aircraft Type
BRITISH AEROSPACE Jetstream 31

ICAO Type Designator
JS31

Airport
Kärdla Airport, Kärdla

Airport ICAO Code
EEKA

An Avies British Aerospace Jetstream 31, registration SE-FVP performing flight U3-2082 from Kardla to Tallinn (Estonia) with 17 passengers and 2 crew, was in the initial acceleration for takeoff from Kardla's runway 14 at about 08:30L (06:30Z) when the left hand engine accelerated to takeoff power while the right engine remained in beta (reverse). The aircraft violently veered to the right and exited the runway about 20 meters down prompting the crew to reject takeoff at low speed. The aircraft came to a stop with all gear on soft ground (grass), the crew subsequently applied power to steer the aircraft onto the paved surface of the nearby taxiway and returned the aircraft to the apron. No injuries occurred, the aircraft did not sustain damage.

The airline confirmed the aircraft veered off the runway due to strong gusting winds and a pilot error which resulted in the engines accelerating asymmetrically.

A replacement Jetstream 31 registration ES-PJD reached Tallinn with a delay of 5 hours.

According to the flight crew operations manuals it is necessary to move the throttle levers back slightly past ground idle (beta) to unlock the propeller blade latches to permit control over the propeller blade pitch angle and permit useful work of the engines. In addition, application of beta range during taxi to slow the aircraft is permitted however discouraged for noise abatement.

Estonia's Safety Investigation Bureau (OJK) released their final report concluding the probable causes of the serious incident were:

The cause of this serious incident is incorrect pilot action on propeller lock disengagement procedure. Pilots did not pull the throttle levers fully to REVERSE position and waited for torque increase, leaving RH propeller starting latches in the engaged position. The condition was left unnoticed by the pilots, resulting in asymmetrical thrust production while applying takeoff power.

Contributory factors

- None of the pilots tried to stop the aircraft exiting the runway by applying the brakes.

- The fact that there is no indication in the cockpit with regards to the position of starting latches has caused pilots to develop and use multiple unofficial procedures to determine the condition of a propeller.

The OJK reported the captain (56, ATPL, 14,500 hours total, 530 hours on type) was pilot flying, the first officer (49, ATPL, 2,500 hours total, 2,000 hours on type) was pilot monitoring. The crew performed before takeoff preparations, while reading the "after engine start" checklist the captain did not reply to the last item, "start locks" referencing the propeller start lock disengagement.

The crew did not notice any anomalies while taxiing for departure, the before takeoff checklist was read and the captain applied takeoff power, which immediately resulted in the aircraft turning sharply right with the crew unable to maintain directional control with nose wheel steering or rudder. While the aircraft exited the runway the captain retarded the power levers to idle and regained directional control about 35 meters from the beginning of the takeoff roll on a grass strip between runway and apron, continued to taxi across the grass onto the apron, where the passengers disembarked.

Following disembarkation of passengers the crew started the engines again, taxied onto the runway and performed a test of engines, propellers and systems without detecting any anomaly.

The OJK reported: "Two hours of erased recordings were recovered from the CVR and sound spectrum analysis was performed. The CVR spectrum analysis reveal, that while the crew went through the After Start check list, the engines were running at approximately at 72% (76Hz). Just after co-pilot reads check-list item „Start Locks”, both engines were briefly brought to 81% (86Hz) and 80% (85Hz) one after the other during the check."

The OJK analysed that there was no technical issue, the investigation therefore focussed on "crew coordination and training aspects".

The OJK analysed: "It is evident from [cockpit voice recording] that even without the Captain replying, there has been some pilot action in order to disengage the start locks. The RPM applied has been enough to overcome the elastic forces of the start lock springs, what appears is, that the power levers were not being moved all the way to the REVERSE position, not waited for torque to increase, thus leaving the RH propeller on the starting locks. The fact that there is no indicator in the cockpit referring to the position of the start latches in the aircraft, the condition was left unnoticed for the flight crew during taxy and takeoff procedures. According to the captain statements – the flight crew did not check the torque indication when disengaging the start locks and the crew was not familiar to the start lock system construction or mechanics. After finishing the before takeoff checklist (at 29:50) pilots apply takeoff power (at 30:10). As the RPM increases, within two seconds (at 30:12) the aircraft banks sharply to the right due to the asymmetrical thrust that is produced by the engines and propellers. LH propeller unlocked from the starting latches and the pitch controllable in the flight range (alpha range), producing takeoff thrust. RH propeller locked on the starting latches in the ground mode (beta range), producing thrust required for ground operations."

Metars:
EEKA 280850Z 22012KT 9999 BKN011 ///// Q0992=
EEKA 280750Z 22008KT 9999 SCT011 ///// Q0992=
EEKA 280650Z 22008KT 9999 FEW011 ///// Q0992=
EEKA 280550Z 24009KT 9999 SCT011 ///// Q0992=
EEKA 280450Z NIL=
EEKA 280350Z 23008KT 9999 BKN009 BKN064 ///// Q0991=
EEKA 280250Z 23009KT 9999 OVC009 ///// Q0999=